Superconducting bearing device

ABSTRACT

A superconducting bearing device for supporting a rotary shaft (rotary body) 2 in a noncontact state for rotation at a high speed. A superconducting bearing 4 for supporting the rotary shaft 2 in a noncontact state relative to a housing 1 comprises permanent magnets 14 mounted on the rotary shaft 2, and Type II superconductors 17 attached to the housing 1 and opposed to the magnets as vertically spaced apart therefrom. A mechanical catcher bearing 21 comprising a thrust ball bearing is disposed between the housing 1 and the rotary shaft 2 at opposed portions thereof. An initial position determining mechanism is provided for lifting a bearing ring 23 of the catcher bearing 21 on the housing 1 to position the housing 1 and the rotary shaft 2 in place relative to each other, whereby the superconductors 17 and the permanent magnets 14 on the shaft 2 can be positioned in place relative to each other. The superconducting bearing 4 can be operated efficiently by suitably determining the relative position. The catcher bearing 21 prevents damage to the rotary shaft 2 and parts therearound when the superconductors 17 of the bearing 4 become normally conductive.

TECHNICAL FIELD

The present invention relates to superconducting bearing devices, forexample, for use in hydraulic machines and machine tools which requirehigh-speed rotation, or power storage apparatus for storing excessiveelectric power as converted to kinetic energy of a flywheel.

BACKGROUND ART

Superconducting bearings devices already known include those disclosed,for example, in the specifications of U.S. Pat. Nos. 4,886,778 and4,892,863.

These superconducting bearing devices have incorporated therein a TypeII superconductor, i.e., a superconductor which permits penetration ofthe magnetic flux of a permanent magnet in a temperature environmentwhich realizes a Type II superconducting state. The superconductingbearing device comprises a permanent magnet mounted on a rotary body,and a Type II superconductor provided on a fixed portion and opposed tothe magnet.

However, the superconducting bearing device has the problem of being lowin operation efficiency since the device has no mechanism fordetermining the position of the superconductor and the permanent magnetrelative to each other when the device is to be initiated intooperation. Further the device has the problem that the rotary body andparts therearound become damaged or broken should the superconductor bemade normally conductive (quenched).

An object of the present invention is to provide a superconductingbearing device which is free of these problems.

DISCLOSURE OF THE INVENTION

The present invention provides a superconducting bearing device adaptedto rotatably support a rotary body by a superconducting bearing in anoncontact state, the rotary body being so disposed as to be movablerelative to a fixed portion in the direction of axis of rotation and ina direction orthogonal to the direction of rotation axis, the rotarybody being rotatable relative to the fixed portion, the superconductingbearing device being characterized in that the superconducting bearingcomprises a permanent magnet mounted on the rotary body, and a Type IIsuperconductor attached to the fixed portion and opposed to the magnet,the permanent magnet being so mounted on the rotary body that therotation of the rotary body will not alter the magnetic fluxdistribution around the axis of rotation of the rotary body, the Type IIsuperconductor permitting the penetration of magnetic flux of thepermanent magnet thereinto in a temperature environment realizing a TypeII superconducting state and being so attached to the fixed portion asto be disposed at a position which is spaced apart from the magnet by adistance permitting a predetermined quantity of magnetic flux thereof topenetrate thereinto and which will not permit the rotation of the rotarybody to alter the distribution of penetrating magnetic flux, opposedportions being provided between the fixed portion and the rotary body toposition the former below the latter, a mechanical catcher bearing beingdisposed at the opposed portions and having a bearing member on thefixed portion side, an initial position determining mechanism beingprovided between the fixed portion and the rotary body for lifting thebearing member to determine the position of the fixed portion and therotary body relative to each other.

Preferably, the mechanical catcher bearing is a thrust ball bearingprovided concentrically with the rotary body, the thrust ball bearinghaving a bearing ring attached to the fixed portion and another bearingring attached to the rotary body, the bearing ring on the fixed portionbeing movable upward and downward.

Alternatively, the mechanical catcher bearing is a thrust slide bearingprovided concentrically with the rotary body and having a slide ringattached to the fixed portion. The slide ring is formed on an uppersurface thereof with an upwardly tapered annular ridge, and is movableupward and downward. The rotary body is concentrically formed in aportion thereof opposed to the ridge with an annular recessed portionapproximately inverted V-shaped in cross section for the ridge to fitin. The slide ring and the recessed portion provide the thrust slidebearing.

With the bearing device described, the permanent magnet and the Type IIsuperconductor of the bearing are held spaced apart by a predetermineddistance as opposed to each other by the restraining action of the fluxof the permanent magnet penetrating into the conductor. In this state,the rotary body carrying the permanent magnet can be rotated about itsaxis. At this time, the magnetic flux penetrating into the Type IIsuperconductor offers no resistance to the rotation insofar as themagnetic flux distribution is uniform about the axis of rotation andremains unaltered. Accordingly, the rotary body can be supported in anoncontact state with respect to the axial direction and radialdirection merely by positioning the permanent magnet provided on therotary body in place relative to the Type II superconductor.

When the bearing member of the mechanical catcher bearing on the fixedportion side is raised by the initial position determining mechanismbefore the bearing device is initiated into operation, the rotary bodyis lifted to position the fixed portion and the rotary body in placeaxially of the rotary body and also with respect to the radial directionorthogonal to the axis of rotation of the rotary body, whereby the TypeII superconductor on the fixed portion and the permanent magnet on therotary body can be set in position relative to each other. When therelative position is determined suitably, the superconducting bearingcan be operated efficiently.

The mechanical catcher bearing is disposed at the opposed portions whichare provided between the fixed portion and the rotary body so as toposition the former below the latter, whereby the rotary body and partstherearound are protected from damage or breakage even if the Type IIsuperconductor should become normally conductive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view in vertical section schematically showing asuperconducting bearing device as a first embodiment of the invention;and

FIG. 2 is a view in vertical section schematically showing asuperconducting bearing device as a second embodiment of the invention.

BEST MODE OF CARRYING OUT THE INVENTION

The present invention will be described below in greater detail withreference to the accompanying drawings. In the following description,likeparts are designated by like reference numerals.

FIG. 1 schematically shows the overall construction of a firstembodiment, i.e., a superconducting bearing device. The bearing devicecomprises a housing (fixed portion) 1 disposed vertically, and avertical rotary shaft(rotary body) 2 which is to be rotatingly supportedin a noncontact state in the center of the housing 1.

Arranged inside the housing 1 are a high-frequency electric motor 3 forrotating the rotary shaft 2 at a high speed, and a superconductingbearing4 positioned below the motor for supporting the rotary shaft 2.

The motor 3 comprises a rotor 5 attached to the rotary shaft 2, and astator 6 disposed around the rotor 5 and attached to the housing 1 by anunillustrated support member.

The superconducting bearing 4 has the following construction. A pair ofhorizontal annular bodies 7, 8 vertically spaced apart by apredetermined distance are fixed to the inner periphery of thehousing 1. The annular bodies 7, 8 respectively have through bores 9, 10vertically extending therethrough centrally thereof. The rotary shaft 2is inserted through these bores 9, 10 with a clearance formedtherearound. The lower bore 10 is smaller than the upper bore 9 indiameter.

Between the upper and lower annular bodies 7, 8, a horizontal disk-linepermanent magnet portion 11 is mounted on the rotary shaft 2concentrically therewith. The magnet portion 11 has a horizontal disk 12fixed to the rotary shaft 2. An annular groove 13 concentric with therotary shaft 2 is formed in each of the upper and lower surfaces of thedisk 12. An annular permanent magnet 14 is fixedly fitted in the groove13. These permanent magnets 14 are so provided that the magnetic fluxdistribution about the axis of rotation of the rotary shaft 2 will notbe altered by rotation.

The two annular bodies 7, 8 are formed with annular hollow portions 15,16,respectively, inside thereof. A plurality of Type II superconductors17 arecircumferentially arranged close to one another at equal spacingsin each of the hollow portions. The superconductors 17 comprise asubstrate made of yttrium high-temperature superconducting material,such as YBa₂ Cu₃ O_(x), and incorporating normally conducting particles(Y₂Ba₁ Cu₁) as uniformly mixed with the material, and having propertiesto restrain the magnetic flux emitted by the permanent magnet 14 andpenetrating thereinto in an environment realizing a Type IIsuperconducting state. The superconductors 17 are arranged at a positionspaced apart from the magnet and permitting a specified quantity ofmagnetic flux of the magnet to penetrate thereinto, the position beingsuch that the penetrating flux distribution will not be altered by therotation of the rotary body 2.

The upper and lower hollow portions 15, 16 communicate with each otherthrough a channel 18 formed in the housing 1. The communication channel18is connected to a cooling unit 20 having a temperature control unit19. A refrigerant such as liquid nitrogen is circulated through thechannel 18 and the hollow portions 15, 16 by the cooling unit 20 to coolthe superconductors 17 with the refrigerant filling up the hollowportions 15,16. Accordingly, the Type II superconductors 17 are broughtinto the Type II superconducting state, and many of the magnetic fluxesemitted from thepermanent magnets 14 of the magnet portion 11 penetrateinto the superconductors 17 and are thereby restrained (pinningphenomenon). With the particulate normal conductor uniformly present inthe superconductors 17, the distribution of fluxes penetrating into thesuperconductors 17 is held constant, with the result that the rotarybody 2 is arrested by the superconductors 17 along with the magnetportion 11 as if the magnets 14 are pierced with phantom pins verticallyextending from the superconductors 17. For this reason, the rotary body2 is supported with respect to the radial and axial directions, as heldlevitated with high stability.

A mechanical catcher bearing 21 comprising a ceramic thrust ball bearingisprovided concentrically with the rotary shaft 2 between the lowersurface of the permanent magnet portion 11 and the upper surface of thelower annular body 8 at opposed portions thereof. The bearing 21 has anupper bearing ring 22 fixedly fitted in an annular groove 25 formed inthe lowersurface of the disk 12 concentrically therewith, and a lowerbearing ring 23 disposed in an annular groove 26 which is formed in theupper surface of the annular body 8 and opposed to the groove 25. Thebearing ring 23 ismovable upward and downward and slightly movableradially. A plurality of balls 24 are arranged between the racewaysurfaces 22a, 23a of the respective bearing rings 22, 23. A lift device27 for moving the bearing ring 23 is disposed inside the groove 26 belowthe ring 23. The lift device 27 comprises, for example, a plurality ofpiezoelectric elements arranged in superposed layers. The mechanicalcatcher bearing 21 and the lift device 27 constitute an initial positiondetermining mechanism for positioning the annular body 8 and the magnetportion 11 in place relativeto each other.

If the superconductors 17 of the bearing 4 should become normallyconductive and unable to afford a support force during operation, theupper bearing ring 22 of the mechanical catcher bearing 21 comes intocontact with the balls 24 arranged on the raceway surface 23a of thelowerbearing ring 23, whereby the rotary shaft 2 in rotation issupported. This precludes damage to or break of the rotary shaft 2 andparts therearound.

During operation, the lift device 27 remains lowered in an operationposition, and the rotary shaft 2 is supported by the superconductingbearing 4 as previously stated, whereby the upper bearing ring 22 isheld out of contact with the balls 24. Further the rotary shaft 2 is inrotation as supported approximately in the center of the housing 1, andthe permanent magnet portion 11 is supported approximately at thevertically middle portion between the two annular bodies 7, 8.

While the device is out of operation, the supply of the refrigerant formthe cooling unit 20 is also discontinued. Accordingly, thesuperconductors17 are in the normally conductive state, producing nosupport force. The rotary shaft 2 is therefore at rest as supported bythe mechanical catcherbearing 21 on the housing 1.

The bearing device thus out of operation is initiated into operation inthefollowing manner.

First, the lower bearing ring 23 of the catcher bearing 21 is raised toa predetermined position by the lift device 27. With the rise of thebearingring 23, the balls contact the raceway surfaces 22a, 23a of therings 22, 23, lifting the rotary shaft 2 to position the lower annularbody 8 and the permanent magnet portion 11 in place with respect to thevertical direction. At the same time, the raceway surfaces 22a, 23a ofthe bearing rings 22, 23 of the catcher bearing 24 and the balls 24thereof contact toposition the annular body 8 and magnet portion 11 inplace with respect to the radial direction. At this time, the upperpermanent magnet 14 is positioned close to the lower surface of theupper annular body 7, and thedistance from the lower surface of theupper annular body 7 to the upper surface of the upper magnet 14 issmaller than the distance from the uppersurface of the lower annularbody 8 to the lower surface of the lower magnet 14.

With the rotary shaft 2 thus positioned, the refrigerant is circulatedthrough the hollow portions 15, 16 by the cooling unit 20 to cool thesuperconductors 17. When the superconductors 17 are refrigerated to thesuperconducting state, a support force is produced as previouslydescribed, so that the initial position determining mechanism 27 islowered to the operation position for the mechanism 27 to afford nosupport, whereupon the rotary shaft 2 slightly lowers under gravity andcomes to a halt at a position where it is in balance with the force ofmagnetic repulsion and pinning force of the superconducting bearing 4.As a result, the magnet portion 11 is supported approximately at thevertically middle position between the two annular bodies 7, 8, and therotary shaft 2 is supported in a noncontact state as previouslydescribed.The rotary shaft 2 is therefore rotated by the motor 3 for thestart of operation.

FIG. 2 schematically shows the overall construction of anothersuperconducting bearing device, i.e., a second embodiment. In this case,amechanical catcher bearing 30 comprising a thrust slide bearing isprovidedconcentrically with the rotary shaft 2 between the lower surfaceof the permanent magnet portion 11 and the upper surface of the lowerannular body 8. The bearing 30 has a slide ring 31 disposed inside theannular groove 26 in the upper surface of the annular body 8 and movableupward and downward and also slightly movable in the radial direction.The slide ring 31 is formed on the upper surface thereof with anupwardly tapered ridge 31a extending along the entire circumference ofthe ring. The lower surface of the disk 12 is formed at the portionthereof opposed to the ridge 31a with an annular groove (recessedportion) 32 approximately inverted V-shaped in cross section, concentricwith the disk and extendingalong the entire circumference for the ridge31a to fit in. The slide ring 31 and the annular groove 32 constitutethe thrust slide bearing. This bearing 30 and the lift device 27constitute an initial position determining mechanism for positioning theannular body 8 and the permanentmagnet portion 11 in place relative toeach other.

Should the superconductors 17 of the superconducting bearing 4 becomenormally conductive and unable to give a support force during operation,the ridge 31a on the slide ring 31 of the catcher bearing 30 comes intosliding contact with the surface defining the annular groove 32 in thelower surface of the disk 12, whereby the rotary shaft 2 in rotation issupported. This prevents damage to the rotary shaft 2 and partstherearound.

The present embodiment is in the same state as the first embodimentduring operation or while out of operation.

When the bearing device as held out of operation is to be operated, theslide ring 31 of the mechanical catcher bearing 30 is first raised bythe lift device 27. With the rise of the slide ring 31, the ridge 31asnugly fits into the annular groove 32, lifting the rotary shaft 2,whereby the lower annular body 8 and the permanent magnet portion 11 arepositioned inplace with respect to the vertical direction and also withrespect to the radial direction. This positions the rotary shaft 2 andthe housing 1 in place relative to each other.

INDUSTRIAL APPLICABILITY

The device of the invention is suitable, for example, for use inhydraulic machines and machine tools which require high-speed rotation,or power storage apparatus for storing excessive electric power asconverted to kinetic energy of a flywheel.

We claim:
 1. A superconducting bearing device adapted to rotatablysupport a rotary body in a noncontact state, the rotary body being sodisposed as to be movable relative to a fixed portion in the directionof an axis of rotation of said rotary body and in a direction orthogonalto the direction of the axis, the rotary body being rotatable relativeto the fixed portion, the superconducting bearing device comprising:apermanent magnet mounted on the rotary body; a Type II superconductorattached to the fixed portion and opposed to the magnet, the permanentmagnet being so mounted on the rotary body that rotation of the rotarybody will not alter magnetic flux distribution around the axis ofrotation of the rotary body, the Type II superconductor permitting thepenetration of magnetic flux of the permanent magnet thereinto in atemperature environment realizing a Type II superconducting state andbeing so attached to the fixed portion as to be disposed at a positionwhich is spaced apart from the magnet by a distance permitting apredetermined quantity of magnetic flux thereof to penetrate thereintoand which will not permit the rotation of the rotary body to alter thedistribution of penetrating of magnetic flux, opposed portions beingprovided between the fixed portion and the rotary body; and an initialposition determining mechanism being provided at the opposed portionsfor positioning the fixed portion and the rotary body relative to eachother so that magnetic flux from the magnet is pinned to thesuperconductor, the initial position determining mechanism comprising anannular portion provided concentrically with the rotary body and a ringwhich is movable in the direction of the axis of rotation, the ringdisposed on the fixed portion and corresponding to the annular portion,a recessed portion and a ridge portion being so provided between theannular portion and the ring as to be related to each other fordetermining the position of the fixed portion and the rotary bodyrelative to each other when the ring is moved in the direction of theaxis.
 2. A superconducting bearing device as defined in claim 1, whereinthe initial position determining mechanism is provided concentricallywith the rotary body, the mechanism having a thrust ball bearing whereina raceway surface is formed respectively on each of the bearing rings, aplurality of balls being disposed between the raceway surfaces of therings, the thrust ball bearing having one bearing ring attached to thefixed portion and the other bearing ring attached to the rotary body,the bearing ring on the fixed portion being movable in the direction ofthe axis of rotation.
 3. A superconducting bearing device as defined inclaim 1, wherein the initial position determining mechanism has a thrustslide bearing provided concentrically with the rotary body, the thrustslide bearing comprising a slide ring attached to the fixed portion andhaving a tapered ridge portion on a surface thereof, and an annularrecessed portion opposed to the ridge portion of the rotary body andconcentric therewith, the annular recessed portion being approximatelyinverted V-shaped in cross section to be engaged with the ridge portion,the slide ring being movable in the direction of the axis of rotation.4. A superconducting bearing device as defined in claim 1, where in theinitial position determining mechanism functions as a mechanical catcherbearing in response to said magnet and said Type II superconductorfailing to support said rotary device.
 5. A process for initiating asuperconducting bearing device into operation, the superconductingbearing device having a superconducting bearing and an initial positiondetermining mechanism;the superconducting bearing comprising a permanentmagnet mounted on a rotary body and a Type II superconductor attached toa fixed portion to be opposed to the magnet and positioned in a magneticfield of the magnet; the permanent magnet being so mounted on the rotarybody that the rotation of the rotary body will not alter the magneticflux distribution around the axis of rotation of the rotary body; theType II superconductor permitting the penetration of magnetic flux ofthe permanent magnet thereinto in a temperature environment realizing aType II superconducting state and being so attached to the fixed portionas to be disposed at a position which is spaced apart from the magnet bya distance permitting a predetermined quantity of magnetic flux thereofto penetrate thereinto and which will not permit the rotation of therotary body to alter the distribution of penetrating magnetic flux; theinitial position determining mechanism being formed at opposed portionsprovided between the fixed portion and the rotary body, the mechanismdetermining the position of the fixed portion and the rotary bodyrelative to each other until the magnetic flux of the permanent magnetis pinned to the superconductor to start the rotation of the rotarybody, the mechanism comprising an annular portion providedconcentrically with the rotary body and a ring which is movable alongthe axis of rotation, the ring disposed on the fixed portion andcorresponding to the annular portion, a recessed portion and ridgeportion being so provided between the annular portion and the ring as tobe related to each other for determining the position of the fixedportion and the rotary body relative to each other when the ring ismoved toward the rotary body; the process comprising the steps of:(a)moving the rotary body by engaging the ring with the ridge portion, anddetermining the position of the fixed portion and the rotary bodyrelative to each other based on a relationship between the recessedportion and the ridge portion, and thereby placing the Type IIsuperconductor at a position which is spaced apart from the permanentmagnet by a distance permitting a predetermined quantity of magneticflux thereof to penetrate thereinto, and magnetizing the Type IIsuperconductor by a magnetic field of the magnet; (b) following the step(a), cooling the Type II superconductor to maintain the Type IIsuperconductor in a temperature environment realizing a Type IIsuperconducting state, and pinning the magnetic flux which waspenetrated into the superconductor; and (c) following the step (b),disengaging the ring so that the ring affords no support for the rotarybody, whereupon the rotary body is suspended stably at a position whereweight of the rotary body is in balance with the force of magneticrepulsion and pinning force of the superconducting bearing.
 6. Asuperconducting bearing device, for allowing for rotation of a rotarybody about an axis of rotation within a fixed portion, the rotary bodybeing movable relative to said fixed portion in the direction of theaxis and in a direction orthogonal to the direction of the axis, thesuperconducting bearing device comprising:a permanent magnet mounted onthe rotary body having a magnetic flux distribution that is symmetricabout the axis of rotation; a Type II superconductor, attached to thefixed portion and opposed to the magnet; opposed portions providedbetween the fixed portion and the rotary body; an initial positiondetermining mechanism, provided at the opposed portions for positioningthe fixed portion and the rotary body relative to each other; and a liftdevice, coupled to said initial positioning device, for adjusting theposition of the rotary body with respect to the fixed portion so as topermit the penetration of a predetermined quantity of magnetic flux ofthe permanent magnet into the superconductor when the superconductor isin a superconducting state, wherein said predetermined quantity of fluxprovides support during rotation of the rotary body so that the rotarybody is out of contact with the fixed portion.
 7. A superconductingbearing device as defined in claim 6, wherein the initial positiondetermining mechanism is provided concentrically with the rotary body,the mechanism having a thrust ball bearing wherein raceway surfaces areformed on upper and lower bearing rings, a plurality of balls beingdisposed between the raceway surfaces of the rings, the thrust ballbearing having one bearing ring attached to the fixed portion and theother bearing ring attached to the rotary body, the bearing ring on thefixed portion being movable in the direction of the axis.
 8. Asuperconducting bearing device as defined in claim 6, wherein theinitial position determining mechanism has a thrust slide bearingprovided concentrically with the rotary body, the thrust slide bearingcomprising a slide ring attached to the fixed portion and having atapered ridge portion on a surface thereof, and an annular recessedportion opposed to the ridge portion of the rotary body and concentrictherewith, the annular recessed portion being approximately invertedV-shaped in cross section to be engaged with the ridge portion, theslide ring being formed on a surface thereof with a tapered annularridge, the annular recessed portion being formed in the rotary bodyconcentrically therewith at a portion thereof opposed to the annularridge for the ridge to fit in, the slide ring being movable in thedirection of the axis.
 9. A superconducting bearing device as defined inclaim 6, where in the initial position determining mechanism functionsas a mechanical catcher bearing in response to said magnet and said TypeII superconductor failing to support said rotary device.